The aim of this program project proposal is to pursue research in basic and clinical aspects of neurophysiology and neuropsychology relevant to an increased understanding of mental retardation and related aspects of human development. This aim will be implemented by utilizing the talents of a group of researchers in a cooperative and collaborative manner. Members of this group will undertake the following tasks: 1. The application of behavioral, electrophysiological and morphologial techniques in studies of normal development in animals and of alterations in normal development as a consequence of neonatal brain insult or environmental manipulation. These studies are designed to elucidate the neural bases of impaired performance and to provide animal models of species of mental retardation. 2. A study of the mechanisms underlying normal and abnormal aspects of learning including investigations of the cellular bases of plastic behavior and, where possible, correlation of cell membrane physiology with ultrastructural analysis. 3. Parallel studies in human subjects and in animals designed to investigate auditory information processing in the normal and abnormal brain with the long-range goal of understanding the nature of abnormal auditory processing in the retarded human. 4. The provision of a milieu for attracting and training young scientists in related research areas.